Is there any way to forward a Distribution List in Outlook?

I'm trying to forward a distribution list that I have, to some people
outside our company. So..I open the Distribution List, I select the Action
menu on the toolbar and select Forward from the drop down menu. It creates a
new email with an attachment (I'm assuming this is the list in some sort of
format) and I sent it.

What is strange is that althought the people outside the company are getting
my email, the attachment is not there. Am I missing a step?

Do they need Exchange/Outlook to receive this Distribution List?

Is there something on my Exhange Server that might be stripping out that
attachment?

OR....Is there something on the recipients' Email Servers that might be
stripping out that attachment?

Thanks